void IP(unsigned char *, unsigned int *);
extern unsigned int packet_len;
extern unsigned int ip_len;
extern unsigned int ip_checksum_loc;
extern unsigned int ip_checksum;
#define IP_VER 0x45
#define DSFIELD_ICMP 0x0
#define DUMMY_IDENTIFICATION 0x0
#define FLAGS 0x2
#define JOIN(entry1, entry2) (((entry1 << 8) & 0xff00) | (entry2 & 0xff))

